This invention regards a releasable fastening device for an object that in the fastening area is bar-shaped and has a cross section with a round or non-round peripheral shape, e.g. a Christmas tree, a square fence post or a candle. The invention is initially intended for, but not limited to, a vertically or approximately vertically upright item, e.g. a Christmas tree.
There are several known fastening devices for bar-shaped objects in existence. In some cases, the object is fastened in a cylindrical holder/socket by means of screws that are screwed into the object.
In another case, described in DE 19545787, the object is fastened in a cylindrical socket that has been split lengthwise into two parts of identical size, where the two semi-cylindrical parts are hinged together on one side. The object is then placed between the parts, whereupon these are closed and locked, e.g. with a locking pin. The insides of these semi-cylindrical parts, and possibly the bottom of the fastening device, may if desired be provided with teeth, points or mouldings that bite into or grip the object in order to keep this in place.
In GB 1589257, a fastening device with fastening levers is used, which at the end is equipped with teeth or similar that bite into the object and keep it in place. At the other end, said levers are fastened, or possibly hinged, to an annular element wherein the object is placed and centred. Each lever may as an example rotate about a shaft that is attached to the annular element, so that the rotational movement occurs within an imaginary vertical plane that extends radially from the centre of the annular element. The fastening levers are provided with teeth, points or similar at the end that interacts with the object.
In U.S. Pat. No. 4,949,502 and EP 96081 the fastening levers have at the opposite end been extended past a rotational shaft, where this end is designed so as to form one of several legs upon which the object can stand. After the fastening levers have been brought into engagement with the object, the weight of the object will give the fastening levers a moment about said rotational shaft, which moment will force the legs outwards in the radial direction. At the same time, the other end of each fastening lever is forced in towards the object, keeping this clamped.
Known devices as described above have disadvantages of a varying nature. The fastening device where the object is fastened in a cylindrical holder/socket by means of screws that are screwed into the object, e.g. a Christmas tree, often requires that one bends down, or possibly crawls underneath the object, in order to tighten or adjust the screws. The associated screw thread may also rust, for instance in connection with watering a Christmas tree. This may cause problems when fastening or loosening the screws.
The fastening device where the object is fastened in a cylindrical socket that has been split lengthwise into two parts, and where the two semi-cylindrical parts are hinged together on one side, requires that the part of the object that is fastened in the cylinder has a shape and size that fits into this.
Some of the fastening devices that keep the object in place by means of fastening levers have the disadvantage of not allowing the object to be lifted and moved without the object detaching from the fastening device.
The object of the invention is to provide a fastening device that makes it easy to fasten and release an object with a bar-shaped fastening area and a cross section with a round or non-round peripheral shape. The invention also seeks to provide a fastening device that allows the object to be moved without detaching from the fastening device.
The object is achieved through the characteristics stated in the description given below and the subsequent claims. Advantages of the invention will also be seen from the description and the subsequent claims.
According to the invention, the fastening device consists of a base with an optional exterior shape, which internally consists of a cylindrical or conical through-going or not through-going opening that runs to a centring point positioned at the bottom of the base. As an alternative to a centring point, it is possible to utilise another suitable centring device in order to keep the object centred in the opening. The lower part of the base also functions as a foot, while the upper part houses a releasable fastening mechanism. The inside of the upper part of the base, which may be shaped like a collar, has been designed with said cylindrical or conical opening. This part of the base contains one or several recesses or enlarged portions of a suitable shape, which are open at the top of the base. Underneath the recess(es) or the enlarged portion(s), the wall of the opening has a circular and preferably horizontal abutment surface, on which surface is placed a separate and matching annular element.
One or several releasable clamping parts are fixed to the annular element in an appropriate manner, which parts are from now on called clamping parts and which coincide with the recess(es) or the enlarged portions(s) in the wall with regard to number and mutual angular spacing. Each clamping part may rotate or be resilient about the fastening area of the annular element, so that the rotational movement occurs within an imaginary vertical plane that runs through the fastening area and radially in towards the centre of the annular element. When fastening an object, the clamping part(s) are preferably placed over the annular element, and the clamping part(s) squeeze the object and keep it clamped.
Each clamping part is further equipped with an integrally cast or affixed outside abutment surface that abuts the inside of the wall material in order to keep the object clamped in the sideways direction. The abutment surface(s) preferably exhibit low friction, in order to allow the object to be rotated about the centreline of the opening with ease.
Each clamping part preferably exerts a spring action in relation to the object to be fastened. The free end of each clamping part that closes against the object may therefore consist of a resilient portion, e.g. a steel spring, while the remainder of the clamping part may consist of a non-resilient portion. The resilient portion may for instance be integrally cast in the clamping part, or it may be attached to this by means of a snap-in type device. The same spring action may be achieved by the resilient portion being rotatably attached to the annular element, where the non-resilient part forms the free end of the clamping part against the object. A third possibility entails the entire clamping part being a resilient portion, for example a steel spring or a resilient plastic element, which is hinged to or non-rotatably attached to the annular element.
The free end, or nose end, of the clamping part, which end upon fastening presses against the bar-shaped object, may be provided with points, teeth, barbs or any other suitable shapes that project in towards the centreline of the opening and create a back stop or an appropriate abutment surface that bites into, grips or engages the object and keeps it clamped.
In order to be able to lift and move the object together with the base, the annular element must be locked to the base in the axial direction of the opening. This may as an example be achieved through providing the annular element with a circular groove or tongue that interlocks with a corresponding tongue or groove in the wall. Additional types of locking devices may be used for this purpose, e.g. a snap-in device, a bayonet coupling or a threaded connection. Each clamping part can also be hinged centrally in the annular element, where the end of the clamping part that does not bite into the object is shaped with a gripping device that bites into, grips or engages a correspondingly shaped edge, ring, moulding or similar in an engagement area of the base, preferably in the opening of the base. In the latter case, lifting the fastened object will cause axial forces to be transferred through the clamping part to said engagement area, so that the forces do not load the hinge device of the clamping part with the annular element.
It is advantageous to all the above mentioned axial locking devices that they be formed in such a way that the annular element may easily be rotated about the centreline of the opening.
The size of the annular element, as well as the number and design of the clamping parts, will naturally place certain restrictions on potential applications with regard to the size, peripheral shape and/or material of the object. These 30 disadvantages may to a certain degree be eliminated by replacing the annular element and the associated clamping part with a corresponding annular element with e.g. a smaller inside diameter, and more or fewer clamping parts, which may also possibly be shaped differently.
When fastening an object, this is inserted into the opening towards or between one or several resilient portions, whereupon the bottom of the object is held in place e.g. by a centring point provided below the annular element, or possibly at the bottom of the base. The resilient portions are elastic, and will therefore take shape according to the peripheral shape of the object, while a back stop or a suitable abutment surface keeps the object in place in the longitudinal direction of the object. The fastening device according to the invention thereby makes it possible to lift and move an object with ease, without the base with associated fastening device detaching and falling off.
When releasing an object from the fastening device, the object is gripped while the base is kept in place, e.g. by using the foot. Then the object is rotated with the annular element and associated parts, preferably about the centreline of the opening, to a position in which the clamping part(s) align with the recess(es) or enlarged portion(s) of the wall, whereupon each clamping part and corresponding resilient portion lose their point of abutment against the wall, loosen from the object and fall outwards through the recess(es) or the enlarged portion(s). The recess(es) or the enlarged portion(s) do not necessarily have to be larger than to allow the free end/nose section, which closes against the object upon release, to move outside of the inner circumference of the annular element. After release, the object is lifted out of the opening in the base and removed.
A further development of the invention may be to adapt the fastening device to various types of objects with regard to size, shape and types of materials. Such a releasable fastening device may also be used in a fastening device in which the object does not stand upright. Examples of this may be a releasable fastening device used as fishing rod holder in a boat, when securing a piece of wood in a lathe, or to anchor an object that is suspended from a ceiling.